There are a wide variety of methods of marking ophthalmic lenses. Some involve the selective removal of the ophthalmic lens material and/or coatings thereon, namely by mechanical engraving and etching and by means of lasers and excimers. Such markings are generally visible to the naked eye with or without special lighting conditions and may be colored with pigments for enhanced visibility. Eyeglass wearers have objected to such permanent markings which can be seen when the eyeglasses are worn. The same holds for colored transfer and photochromic markings in or on the body of the lens material.
Other kinds of markings are normally invisible but can been rendered visible by fogging the lens, in practice, simply by exhaling against the lens to produce a thin layer of condensation. Essentially such methods involve the change in the surface characteristics of the lenses. Some known coatings have high surface energies such as anti-reflective coatings. Others, such as top coats used as anti-smudge coatings to avoid dust and grime collecting on the lens have low surface energies. Typically the high or low surface energy material is selectively chemically modified or even removed to the configuration of the indicia desired. Fogging reveals the low surface energy parts as light colored droplets and the high surface energy parts as darker colored condensate film.
Danielos et al. U.S. Pat. No. 4,912,298 discloses a method of producing a marking on a spectacle lens by irradiation of defined regions of the spectacle lens with a high energy excimer laser through a suitably cutout metal mask spaced from or on the lens which vaporizes a thin layer (0.1 .mu.m ) of a lens so that the marking is recognizable as a breath mark.
In European patent application No. 0 031 633 indicia are provided on a lens surface of a polycarbonate lens by applying concentrated sulfuric acid by means of a printing block, pencil or brush to increase the surface energy of the marked portion and visible when fogged with one's breath. Such a method does not admit of precise delineation of the marked portion and also requires careful washing and drying.
French patent application publication No. 2,727,649 discloses a method of marking eyeglass lenses of organic material with or without antiscratch coating or metallic reflective coatings. This method involves subjecting the face of the lens to be marked to a corona discharge, a flame or ionized air in order to increase the surface energy and thereby improve adherence of the surface to be marked. The actual marking is produced by pad transfer or silk screening printing with a special marking ink comprising an ink and an anti-fogging agent, which is then dried and thereafter the ink component is removed with an appropriate solvent.
European patent No. 0.472.303 concerns a hydrophobic contact lens casting mold, e.g. of polyolefin, which is subject to a hydrophilizing treatment, namely by means of an electrical corona discharge to enhance the adhesion of a hydrophilic monomer coloring dispersion without interference with the release properties of the mold.